1. Field of the Invention
This invention relates, in general, to combustion devices and, in particular, to a new and useful adjustable conical nozzle for the fuel constituents in which a compressed fluid, such as steam or air is used to accelerate an incompressible fluid or liquid such as oil or water. More particularly, the present invention is directed to a dual fluid atomizer in which the compressible fluid, such as steam or air, accelerates an incompressible fluid or liquid, such as oil or water, to a high speed.
In dual fluid atomizers, acceleration of a liquid stream is usually accomplished by mixing a high speed compressible fluid stream with a slower speed liquid stream. This process subjects the liquid to a strong shearing force that breaks it into small droplets. Most known atomizers are either: (1) external mixing atomizers, in which two fluid streams are mixed primarily outside of the structure of the atomizer; or (2) internal mixing atomizers in which the two fluid streams mix primarily inside the main structure of the atomizer.
A disadvantage of some of the known atomizers is that the atomized mixture is directed from one or more mixing holes in the form of concentrated jets. The jets are highly localized and provide less-than-optimum dispersion of the atomized mixture. Consumption of compressible fluid by an atomizer is largely determined by the geometry of the atomizer, including the hole sizes and arrangements, and these characteristics can importantly influence the atomization fineness, turn-down ratio and cost of operation.
In one type of internal mixing atomizer, the two fluid streams are introduced through separate holes at a point inside the atomizer and those holes intersect at an angle and merge into a third hole. The mixing and acceleration process takes place primarily in the third hole and the dual fluid mixture is released from the mixing hole at high speed into the surroundings, so that further shearing may take place between the liquid and the surroundings. Such conventional multi-hole atomizers produce a spray pattern comprising distinct jets separated by voids. When the flow of liquid fuel is reduced or turned down, the jets become thinner and the voids become larger. When such a fuel atomizer is used in combination with an optical flame detector, the thinning of the jets in the spray pattern can cause an erroneous loss of ignition indication from the flame detector.